Errors in 14 pulse oximeters during profound hypoxia

Abstract

The accuracy of pulse oximeters from fourteen manufacturers was tested during profound brief hypoxic plateaus in 125 subject sets using 50 normal adult volunteers, of whom 29 were studied two to nine times. A data set usually consisted of 10 subjects, and 13 sets were collected between August 1987 and July 1988. In the first 6 sets, six 30-second hypoxic plateaus were obtained per subject at 55 +/- 6% oxyhemoglobin (O2Hb) (range, 40 to 70%). In the last 7 sets, three hypoxic plateaus were obtained at each of four levels, approximately 86, 74, 62, and 50% O2Hb, for the purpose of linear regression analysis. Inspired oxygen was adjusted manually breath by breath in response to arterial oxygen saturation computed on-line from end-tidal oxygen and carbon dioxide tensions. End-plateau arterial blood O2Hb was analyzed by a Radiometer OSM-3 oximeter, and plateau pulse oximeter saturation (SpO2) was read by cursor from a computer record of the analog output. Three to 13 instruments were tested simultaneously by using 1 to 3 duplicate instruments from each of one to seven manufacturers. Variations introduced by manufacturers were tested on subsequent sets in several instruments. An index of error, "ambiguity" (alpha) of oxygen saturation, was defined as the absolute sum of bias and precision (mean and SD of SpO2 - O2Hb) at O2Hb = 55.8 +/- 4.5%, preserving the sign when bias was significant at P less than 0.05. Ambiguity values for finger probes (unless specified) with latest data were: Physio-Control, 3.9 (ear, 3.3); Puritan-Bennett, -4.4; Criticare, 5.8 (forehead, 4.7); Kontron, 5.9 (infant probe) and 6.1 (ear, 5.8; forehead, 7.1); Biochem, -6.0; Datex 6.4 (ear, 6.9; forehead, 6.8); Critikon, 8.4; SiMed, 8.6; Marquest, 9.0; Novametrix, 10.2; Invivo, -12.2 (ear, -14.3); Nellcor, -15.1; Ohmeda, -21.2; and Radiometer, -21.2 (ear, -9.6). Linear regression slopes of 36 instruments from twelve manufacturers generally deviated from 1 in proportion to alpha. The data showed substantial differences in bias and precision between pulse oximeters at low saturations, the most common problems being underestimation of saturation and failing precision.

Accuracy and reliability of pulse oximetry at different arterial carbon dioxide pressure levels

“…Oximeters from different manufacturers show small differences related to the algorithms used to determine Sp,O 2 from the raw measurements of red and infrared light transmitted through the tissues. These differences were greater in the early days of oximetry than they are now because the current technical characteristics and performance of the majority of pulse oximeters are quite similar [6,7,[32][33][34]37] and all will be equally affected by the various factors known to alter the accuracy of Sa,O 2 measurements. Although the effect of Pa,CO 2 on the accuracy of these devices has not been systematically assessed, it is likely that the present findings can be generalised to other models.…”

The desaturation response time of finger pulse oximeters during mild hypothermia*

“…Severinghaus et al [9] noted response times of 10-20 s for the ear and 24-35 s for the finger oximeters. Similarly, Trivedi et al [7] showed that the ear and forehead sensors performed consistently better than the finger sensors with mean desaturation response times of 38 s, 42 s and 57 s, respectively.…”

The effect of pulsating arteries on reflectance pulse oximetry: Measurements in adults and neonates

“…Severinthe photodiode above a superficial artery results in ghaus et al [7] evaluated three experimental reflectance falsely low Spo2 readings. Reflection pulse oxim etry can pulse oximeters (Criticare, Datex, and Kontron) that be a possible alternative w hen conventional transm iswere placed on the forehead.…”